Tamper indicating bags are used to transfer valuable or sensitive contents. These are usually plastic bags which provide some type of indication if the bag has been opened in transit. Thus, from the point of sealing to the point of delivery, no one should be able to access the bag and remove its contents without being discovered.
There are many different tamper indicating bags. Most of these have openings in the top edge of the bag with an upper flap which can be folded over and adhere to the bag closing the opening. Exemplary bags are disclosed in Whelan, U.S. Pat. No. 4,483,018, Sack et al., U.S. Pat. No. 4,509,196, Sack, U.S. Pat. No. 4,510,621, Wilson, U.S. Pat. No. 4,785,940, Voto, U.S. Pat. No. 4,988,547, Edelman et al., U.S. Pat. No. 4,941,196, Makrauer, U.S. Pat. No. 5,620,256.
Generally the adhesive on the upper flap has some type of printing beneath it. Thus, if someone tries to pull the flap from the bag, frequently using refrigerants to make the adhesive brittle, it will pull the printing off and be detectable.
Frequently these flaps are separately formed and welded to the upper portion of the bag. Alternately the bag itself can be formed with a flap portion which is subsequently coated with an adhesive. These separately formed flaps are expensive relative to the cost of the bag.
Further, a thief can frequently access the contents of a bag through a very small opening that might remain at the very top. Thus, with top-opening bags, if the bag is not properly sealed, it will not be tamper-proof.
A side seal bag is disclosed in WO-91/15406 entitled Security Bag Sealed by Silicone Rubber Adhesive. This reference discloses a side seal bag which is formed by folding a sheet of plastic on itself to form a front side and a rear side. The rear side is longer than the front side and provides an upper flap. A slit is formed in the front side below the top edge to form a side opening bag. Adhesive on the flap is designed to cover the opening. There is also a layer of printing immediately below where the adhesive would contact the pouch. Thus if someone were to use solvent to access the contents, they would dissolve a portion of the printing, thereby being detected.
This reference fails to disclose any method of manufacturing the bag. Further there is no disclosure of forming any indicia over the opening itself where the adhesive would bond to the bag. This is quite critical but is obviously problematic with a side seal bag where the adhesive is designed to cover both above and below the opening. The bag disclosed in this reference would fail to detect a refrigerant used to disable the adhesive.